An internal combustion engine mounted on a vehicle or the like typically has a resonator for reducing noises due to intake pulsing generated in an intake system by the introduction of air thereinto. A resonator construction for this type of internal combustion engine is shown in FIG. 10. In the figure, the reference numeral 202 indicates an air cleaner for an internal combustion engine located in an engine compartment of a vehicle (not shown).
The air cleaner 202 is provided by successively connecting thereto an air cleaner intake hose 204, an air cleaner intake pipe 206, and an air suction case 208 at the upstream side thereof. Air is introduced into the air cleaner 202 by the air suction case 208. The air suction case 208 has an upstream resonator 210 connected thereto.
Also, an air cleaner outlet hose 212, an air intake pipe 214, and an air intake hose 216 are successively connected to the air cleaner 202 at the downstream side thereof. The air intake hose 216 is connected to a throttle body (not shown in FIG. 10), and the throttle body is connected to a surge tank for an intake manifold (also not shown in FIG. 10).
Connected to the air cleaner outlet hose 212 is a downstream resonator 218. Connected to the air intake pipe 214 is a breather pipe 220 for introducing blow-by gas. The reference 222 indicates a cooling water pipe for cooling the breather pipe 220.
As described above, the internal combustion engine includes resonators 210, 218 connected at the respective upstream side and downstream side from the air cleaner 202 so as to control noise due to air intake pulsing. The resonator 218 connected at the downstream side of the air cleaner 202 is connected upstream from a bellows section 224 of the air cleaner outlet hose 212, as well as upstream from the breather pipe 220 connected to the air intake pipe 214.
Resonator constructions for internal combustion engines similar to that described above are disclosed in Japanese Patent Laid-Open Publication Nos. 1993-272421, 1989-159125, and 1994-22558.
The disclosure in Japanese Patent Laid-Open Publication No. 1993-272421 is realized by setting a relation between a drive frequency f1 of duty control for a control valve for adjusting a flow rate of a bypass route for bypassing a throttle valve and a specific number of vibrations f2 of an air intake route from an air cleaner to a throttle valve so that the relation therebetween will be as follows: (3/4.multidot.f1.ltoreq.f2.ltoreq.(5/4).multidot.f1, and by connecting a resonance chamber having a specific number of vibrations substantially equivalent to the drive frequency f1 to the air intake route between the air cleaner and the throttle valve.
The disclosure in Japanese Patent Laid-Open Publication No. 1989-159125 has an air intake device comprising a first independent air intake route branched from a surge tank extending in a specified direction and which communicates with each cylinder, a measurement chamber formed inside a bend section of this first independent air intake route, a second independent air intake route for communicating between this measurement chamber and the first independent air intake route, and a control valve for opening and closing this second independent air intake route. A port for introducing air into the surge tank and a communicating route for communicating between the surge tank and the measurement chamber are also provided, and this communicating route is provided in the surge tank along the direction to which the surge tank is extended as well as close to the inner side of the bend section of the first independent air intake route.
The disclosure in Japanese Patent Laid-Open Publication No. 1994-22558 is realized by attaching a resonator for suppressing pressure pulsing with a connecting edge thereof open to an intake manifold collector having an air cleaner at the upstream side thereof and with the downstream side thereof connected to a cylinder head.
In recent years, engine room space in vehicles has been reduced. For this reason, it is difficult to insure a space for placing a resonator 218 of a resonator construction for an internal combustion engine with the resonator 218 connected to the air cleaner outlet hose 212 at the downstream side of the air cleaner 202.
Also, when the resonator 218 is connected at the downstream side of the air cleaner 202, it is necessary to connect the resonator to the air cleaner outlet hose 212 at a location upstream from the bellows section 224 thereof, so that influence from vibrations propagated from the internal combustion engine over the resonator is avoided and any problems relating to the strength or effectiveness of the resonator will not occur.
However, it is sometimes the case in a resonator construction for a conventional type of internal combustion engine, that it is difficult to insure a space for a resonator 218 with a form largely projecting to the outside, in the engine room due to reduction of the space therein as described above. Further, the resonator cannot be connected upstream from the bellows section 224 of the air cleaner outlet hose 212, and in this case, noises due to intake pulsing cannot be reduced.